1. Field of the Invention
The present invention relates to a method of generating a mask pattern for manufacturing a semiconductor apparatus and a manufacturing method of the semiconductor apparatus.
2. Description of the Related Art
In recent years, a semiconductor manufacturing technique has made very remarkable progress, and semiconductors each having a minimum processed dimension of 0.18 μm have been mass-produced. Such miniaturization is realized by rapid progress of fine pattern forming techniques such as a mask process technique, optical lithography technique, and etching technique. With a sufficiently large pattern size, the technique includes: drawing a plane shape of an LSI pattern to be formed on a wafer as a designed pattern; generating a mask pattern faithful to the designed pattern; transferring the mask pattern onto the wafer by a projection optical system; and etching a foundation, so that the pattern can be formed on the wafer as designed. However, with progress of the miniaturization of the pattern, it has been difficult to form the pattern faithfully in each process, and a problem has occurred that a final finished dimension is not faithful to the designed pattern.
Particularly in lithography and etching processes most important for achieving a fine processing, other pattern layout environments around the pattern to be formed largely influence the dimension precision of the pattern. To reduce these influences, techniques (hereinafter referred to as PPC techniques) such as an optical proximity correction (OPC) technique for adding an auxiliary pattern beforehand to the designed pattern so that the processed dimension is formed in a desired pattern, and a process proximity correction (PPC) technique are reported in Jpn. Pat. Appln. KOKAI Publication No. 1997-319067 and SPIE Vol. 2322 (1994) 374 (Large Area Optical Proximity Correction using Pattern Based Correction, D. M. Newmark et. al).
The PPC technique is largely classified into two techniques: including a rule based PPC technique of ruling a correction value in accordance with a certain standard and correcting the pattern based on the rule; and a model based PPC technique of using a simulator which can estimate a finished shape on the wafer passed through mask, lithography and etching processes to calculate the correction value. In the rule based PPC technique, a high-speed correction is possible, but it is difficult to perform a high-precision correction. In the model based PPC technique, although the high-precision correction is possible, complicated calculations such as optical simulation are required, much time is therefore required to calculate the correction value, and a turnaround time (TAT) of mask generation is lengthened.
To shorten the time for correction value calculation, the above-described known examples have proposed the following method so that the correction value calculation time is reduced. One example of the method is shown in FIG. 11.
Step S501
A reference point is set in a designed layout, and an area centering on the reference point and having a certain size is cut out. In the Jpn. Pat. Appln. KOKAI Publication No. 1997-319067, it is described that the reference point is determined “in accordance with a surrounding layout”. It is described in SPIE that the reference point is determined “in accordance with a corner or line segment”.
Step S502
A database (hereinafter referred to as a correction value library) in which an edge coordinate group (hereinafter referred to as a correction environment) included in the area and the correction value for the correction environment are stored is checked. This correction value library is searched for the correction environment which agrees with the correction environment cut out in the step S501.
Step S503
If there is the agreeing correction environment, the corresponding stored correction value is referred to and the correction is performed.
Step S504
If there is no agreeing correction environment, the correction value is calculated by the optical simulation, process simulation, and equations such as a polynomial equation representing the correction value. Subsequently, the corresponding correction environment and correction value are added to the correction value library.
All the reference points are subjected to the process of the steps S501 to S504, and the generation of a mask pattern ends.
In this correction method, the correction environment which has appeared once and the corresponding correction value are stored in the correction value library. Therefore, even when the same environment appears again, it is unnecessary to calculate the correction value. As a result, as many simulations requiring much time as possible can be reduced, and it is therefore possible to reduce the generation time of the mask pattern.
In actual device development, small-scaled design data is first generated for purposes of device characteristics measurement and process flow construction, and the mask is generated based on the data. Thereafter, a product for mass production is developed, and further a product derived from the product (hereinafter referred to as a derivative product) is sometimes generated. These small-scaled data and types of the pattern layout for use in the product for mass production or the derivative product are not necessarily different, and there are a large number of redundant pattern types. Moreover, during the device development, a mask is frequently revised with condition changes of fine processing processes such as mask, lithography, and etching.
Under these circumstances, when a conventional mask pattern process is performed, problems delaying TAT of mask generation are considered as follows. First, the correction value library of a generation start time of the mask pattern does not include the edge coordinate group and the corresponding correction value. Therefore, a percentage with which the correction value is obtained by the simulation of the inputted edge coordinate group is very high. Therefore, with a larger scale of the design data, the number of simulated correction environments increases, and this is a cause for deterioration of TAT of mask generation.
Moreover, in the conventional method, it is necessary to newly generate the correction value library again even during the revision of the mask. A method of efficiently using the correction value library in consideration of the above-described circumstances has not been proposed.
As described above, at the start of the generation of the mask pattern, the edge coordinate group and the corresponding correction value are not inputted in the correction value library, a percentage with which the correction value is calculated by the simulation is high, and there is a problem that the TAT of the mask pattern generation is deteriorated.
Moreover, in the conventional method, it is necessary to newly generate the correction value library again even during the revision of the mask, and a method of efficiently using the correction value library in consideration of the circumstances has not been proposed.